The invention relates to a power detection method and related communication device, and more particularly, to a power detection method and related communication device that detects power of RF signal without any oscillator in the demodulator, so as to save hardware costs of the communication device.
A communication device may alternatively use polar transmitter for communication systems such as Global System for Mobile Communications (GSM) and Enhanced Data Rates for GSM Evolution (EDGE) instead of using direct-conversion transmitter (DCT). A polar transmitter offers some advantages, such as a potential for reducing complexity and current consumption in the modulator path as well as eliminating the problem of image rejection, thus the polar transmitter is more suitable for implementation in advanced complementary metal oxide semiconductor (CMOS) processing technologies. More specifically, the polar transmitter is a transmitting device that splits a complex baseband signal explicitly represented by an amplitude-modulated (AM) contented component and a phase-modulated (PM) contented component, instead of an in-phase component and a quadrature component. These two components are then recombined into a radio-frequency (RF) output to be transmitted over the air. For example, an all-digital phase locked loop (ADPLL) may be disposed in a phase modulating path to generate a PM signal, such as a clock output of a digitally-controlled oscillator (DCO), in response to the PM contented component, and the frequency/phase modulated clock is processed by a following stage such as a digitally-controlled power amplifier (DPA).
In the communication device, the transmitter and the demodulator may be connected for power detection of RF signal by utilizing a loopback circuit. Please refer to FIG. 1, which is a schematic diagram of a communication device 10 with power detection scheme according to the related art. The communication device 10 includes a transmitter 100, a demodulator 102 and a loopback circuit 104. The transmitter 100 is used for transmitting an RF signal RF_sig, which includes a PM contented component and an AM contented component. The RF signal RF_sig is transmitted to the demodulator 102 through the loopback circuit 104. The demodulator 102 is used for demodulating the RF signal RF_sig, so as to obtain power information corresponding to the RF signal RF_sig for power calibration. However, in the related art, an oscillator is required in the demodulator 102 to correctly demodulate the RF signal RF_sig, such that the hardware cost of the communication device 10 rises.